Correspondent banks are financial institutions that act as an agent on behalf of other financial institutions, usually foreign banks. Correspondent banks may perform number of functions like Treasury services, manage foreign exchange, manage international investments and facilitate international trade and finance on behalf of the foreign bank.
Nostro and Vostro refers to the same account only but seen with a different perspective.
Nostro account refers to our account held in the other bank. Vostro account means “your account” with the bank.